Validity of Geochemical Signatures of Abiotic Hydrocarbon Gases on Earth

2021 ◽  
pp. jgs2021-077
Author(s):  
X. Xia ◽  
Y. Gao
Keyword(s):  
Fluid Inclusions ◽  
Carbon Number ◽  
Gas Diffusion ◽  
Granitic Rocks ◽  
Hydrocarbon Generation ◽  
Volcanic Emissions ◽  
Hydrocarbon Gases ◽  
Content Type ◽  
Isotopic Compositions ◽  
Supplementary Material

Abiotic synthesis was hypothesized for the occurrences of hydrocarbon gases with atypical molecular and isotopic compositions. This work provides biotic interpretations on these atypical compositions: 1) microbial CH4 oxidation and CO2-sourced methanogenesis may enrich 13C in hydrothermal CH4; 2) microbial hydrocarbon generation using serpentinization-derived H2 may deplete deuterium in hydrocarbons; 3) three processes may cause isotopic reversal with the carbon number in biotic hydrocarbons: i. the decrease of kinetic isotope effect (KIE) with the increase of carbon number during alkane biodegradation, ii. inverse KIE during the thermal decomposition of higher alkanes, and iii. isotopic fractionation during gas diffusion in rock samples; 4) random scission of long alkyl chains may form the exponential distribution of alkane abundance with respect to carbon number (“Schulz-Flory distribution”); 5) isotopic compositions are often not equilibrated; even if they are, the equilibrium temperatures are not necessarily the same as the temperature of hydrocarbon generation. Case studies demonstrate that previously proposed abiotic hydrocarbon gases in continental serpentinite-hosted seepages, continental or oceanic hydrothermal vents, volcanic emissions, gas fields in volcanic reservoirs, and fluid inclusions in alkaline or granitic rocks were formed with various biotic processes. The occurrence of abiotic hydrocarbon gas with decisive evidence is limited to fluid inclusions in some mantle minerals.Supplementary material: Appendices 1 and 2 and tables S1 and S2 are available at https://doi.org/10.6084/m9.figshare.c.5660278.

Oxygen and Hydrogen isotopic composition of tap waters in France

2021 ◽  
pp. SP507-2020-207
Author(s):  
V. Daux ◽  
B. Minster ◽  
A. Cauquoin ◽  
O. Jossoud ◽  
M. Werner ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Geographical Origin ◽  
Atlantic Coast ◽  
Regional Scale ◽  
Content Type ◽  
Isotopic Compositions ◽  
Manufactured Products ◽  
The Alps ◽  
Supplementary Material ◽  
Hydrogen Isotopic Composition

AbstractThe isotopic composition of oxygen (δ18O), and hydrogen (δ2H) are widely used to locate the geographical origin of biological remains or manufactured products. In this paper, we analyze the distributions of δ18O and δ2H in tap waters sampled across France, and in precipitation interpolated with OIPC and modelled with the isotope-enabled ECHAM6-wiso model. Our aim is to provide isoscapes usable in archaeology and forensics and evaluate if modelled data could be surrogates for measured ones.The δ18O and δ2H in the 396 tap waters sampled vary spatially within a range of 10‰ and 77‰ respectively. Their consistent distributions follow rules summarized by the effects of altitude and distance from the coast. Their variations along the year are small. Therefore, the database provides a solid reference for δ18O and δ2H of the water supply system at the regional scale. The areas with the most uncommon oxygen and hydrogen isotopic compositions (Atlantic coast South of Brittany and the highest elevations in the Alps) are the most accurately traceable areas in provenancing studies.The isotopic compositions of modelled precipitation have the same spatial distributions but different absolute values from those of tap waters. Therefore, our results favour the use of statistical isoscapes rather than GCM-based isoscapes in provenancing studies.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5256034

Fluid evolution along the Patterson Lake corridor in the southwestern Athabasca Basin: constraints from fluid inclusions and implications for unconformity-related uranium mineralization

2021 ◽  
pp. geochem2020-029
Author(s):  
M. Rabiei ◽  
G. Chi ◽  
E.G. Potter ◽  
V. Tschirhart ◽  
C. MacKay ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Fluid Pressure ◽  
Uranium Deposits ◽  
Hydrothermal Conditions ◽  
Content Type ◽  
Athabasca Basin ◽  
Link Type ◽  
Basement Faults ◽  
Supplementary Material

The Patterson Lake corridor (PLC) in the southwestern margin of the Athabasca Basin hosts several high-grade uranium deposits. These deposits are located in the basement up to 900 m below the unconformity surface, raising questions about their affiliation with typical unconformity-related uranium (URU) deposits elsewhere in the basin. Based on cross-cutting relationships four pre- and three syn- to post-mineralization quartz generations were identified. Fluid inclusion analyses indicate that pre-mineralization fluids have salinities ranging from 0.2 to 27.2 Wt% NaCl equiv. (avg. 9.0 Wt%), whereas syn-mineralization fluids have salinities ranging from 8.8 to 33.8 Wt% NaCl + CaCl2 (avg. 25.4 Wt%), with NaCl- and CaCl2-rich varieties. The homogenization temperatures (Th) of fluid inclusions from pre-mineralization quartz range from 80 ° to 244 ℃ (avg. 147 ℃), and from syn-mineralization quartz range from 64 ° to 248 ℃ (avg. 128 ℃). Fluid boiling is indicated by the co-development of liquid-dominated and vapor-dominated fluid inclusions within individual fluid inclusion assemblages (FIA) from the syn-mineralization quartz and is related to episodic fluid pressure drops caused by reactivation of basement faults. Our results indicate that composition and P-T conditions of the ore fluids in the PLC are comparable to those of typical URU deposits in the Athabasca Basin, indicating that the uranium deposits in the PLC formed under similar hydrothermal conditions. Episodic reactivation of basement faults was an important driving force to draw uraniferous fluids from the basin and reducing fluids from the basement to the mineralization sites, forming deep basement-hosted deposits.Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathwaysSupplementary material:https://doi.org/10.6084/m9.figshare.c.5510179

The Changshagou gold deposit, Eastern Tianshan, NW China: Orogenic gold mineralization overprinting a Porphyry gold occurrence

2021 ◽  
pp. SP516-2020-248
Author(s):  
Yihao Liu ◽  
Yun Zhao ◽  
Chunji Xue ◽  
Liang Yu ◽  
Haixia Chu ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Gold Mineralization ◽  
Orogenic Gold ◽  
Quartz Syenite ◽  
Eastern Tianshan ◽  
Content Type ◽  
Tianshan Orogenic Belt ◽  
Supplementary Material ◽  
Homogenization Temperatures ◽  
Orogenic Gold Mineralization

AbstractThe temporal-spatial relationships of porphyry and orogenic gold mineralization in the Eastern Tianshan Orogenic Belt are ambiguous. The newly-discovered Changshagou deposit in this belt contains both porphyry and orogenic gold mineralization, which are characterized by polymetallic-sulfide veinlets and quartz-pyrite veins, respectively. Fluid inclusions in the porphyry mineralization episode were trapped at 290–340 °C with salinities of 3.0–8.0 wt.% NaClequiv. The homogenization temperatures and salinities in the orogenic mineralization episode range from 240 to 300 °C and 1.0–5.0 wt.% NaClequiv. Coexisting V-type and L-type fluid inclusions with similar homogenization temperatures are indicative of fluid immiscibility. The δ18Ow and δDw values range from 7.6 to 9.1 ‰ and −70.9 to −84.0 ‰ in the porphyry mineralization episode, and from 6.4 to 7.1 ‰ and −65.7 to −72.1 ‰ in the orogenic mineralization episode, overlapping magmatic and metamorphic ranges, respectively. The pyrite δ34S values range from 3.5 to 4.9 ‰, falls into the magmatic range. Pyrite in porphyry and orogenic mineralization episodes yield Re-Os isotopes ages of 269.1±2.9 Ma and 257.4±2.4 Ma. The porphyry and orogenic gold mineralizations are genetically associated with the quartz syenite porphyry and Kanggur strike-slip shear activity, respectively.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5635584

scholarly journals Fluid inclusions in buried quartz of the Yanchang sandstone in the Jiyuan area, Ordos Basin, China: Implications for basin evolution and petroleum accumulation

2020 ◽  
pp. 014459872097451
Author(s):  
Wenqi Jiang ◽  
Yunlong Zhang ◽  
Li Jiang
Keyword(s):  
Fluid Inclusions ◽  
Ordos Basin ◽  
Homogenization Temperature ◽  
Burial Depth ◽  
Hydrocarbon Generation ◽  
Rock Interaction ◽  
Yanchang Formation ◽  
Reflection Data ◽  
And Migration ◽  
Vitrinite Reflection

A fluid inclusion petrographic and microthermometric study was performed on the sandstones gathered from the Yanchang Formation, Jiyuan area of the Ordos Basin. Four types of fluid inclusions in quartz can be recognized based on the location they entrapped. The petrographic characteristics indicate that fluid inclusions in quartz overgrowth and quartz fissuring-I were trapped earlier than that in quartz fissuring-IIa and fissuring-IIb. The homogenization temperature values of the earlier fluid inclusions aggregate around 80 to 90°C; exclusively, it is slightly higher in Chang 6 member, which approaches 95°C. The later fluid inclusions demonstrate high homogenization temperatures, which range from 100 to 115°C, and the temperatures are slightly higher in Chang 9 member. The calculated salinities show differences between each member, including their regression characteristics with burial depth. Combining with the vitrinite reflection data, the sequence and parameters of fluid inclusions indicate that the thermal history of the Yanchang formation mostly relied on burial. Salinity changes were associated with fluid-rock interaction or fluid interruption. Hydrocarbon contained fluid inclusions imply that hydrocarbon generation and migration occurred in the Early Cretaceous. The occurrence of late fluid inclusions implied that quartz cement is a reservoir porosity-loose factor.

Volcano-sedimentary processes at Las Derrumbadas rhyolitic twin domes, Serdán-Oriental basin, Eastern Trans-Mexican Volcanic Belt

2021 ◽  
pp. SP520-2021-144
Author(s):  
Marie-Noëlle Guilbaud ◽  
Corentin Chédeville ◽  
Ángel Nahir Molina-Guadarrama ◽  
Julio Cesar Pineda-Serrano ◽  
Claus Siebe
Keyword(s):  
Volcanic Belt ◽  
Debris Avalanche ◽  
Density Currents ◽  
Content Type ◽  
Mexican Volcanic Belt ◽  
Wide Range ◽  
Eruptive Episode ◽  
Basin Floor ◽  
Supplementary Material ◽  
Trans Mexican Volcanic Belt

AbstractThe eruption of the ∼10 km3 rhyolitic Las Derrumbadas twin domes about 2000 yrs ago has generated a wide range of volcano-sedimentary deposits in the Serdán-Oriental lacustrine basin, Trans-Mexican Volcanic Belt. Some of these deposits have been quarried, creating excellent exposures. In this paper we describe the domes and related products and interpret their mode of formation, reconstructing the main phases of the eruption as well as syn-and-post eruptive erosional processes. After an initial phreatomagmatic phase that built a tuff ring, the domes grew as an upheaved plug lifting a thick sedimentary pile from the basin floor. During uplift, the domes collapsed repeatedly to form a first-generation of hetero-lithologic hummocky debris avalanche deposits. Subsequent dome growth produced a thick talus and pyroclastic density currents. Later, the hydrothermally-altered over-steepened dome peaks fell to generate 2nd generation, mono-lithologic avalanches. Subsequently, small domes grew in the collapse scars. From the end of the main eruptive episode onwards, heavy rains remobilized parts of the dome carapaces and talus, depositing lahar aprons. Las Derrumbadas domes are still an important source of sediments in the basin, and ongoing mass-wasting processes are associated with hazards that should be assessed, given their potential impact on nearby populations.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5752296

Jurassic–Cretaceous arc magmatism along the Shyok–Bangong Suture from NW Himalaya: Formation of the peri-Gondwana basement to the Ladakh Arc

2021 ◽  
pp. jgs2021-035
Author(s):  
Wanchese M. Saktura ◽  
Solomon Buckman ◽  
Allen P. Nutman ◽  
Renjie Zhou
Keyword(s):  
Late Cretaceous ◽  
Nw Himalaya ◽  
Content Type ◽  
Magmatic Arc ◽  
Basement Rocks ◽  
Ladakh Himalaya ◽  
Accreted Terranes ◽  
Volcaniclastic Rocks ◽  
Supplementary Material ◽  
Depositional Age

The Jurassic–Cretaceous Tsoltak Formation from the eastern borderlands of Ladakh Himalaya consists of conglomerates, sandstones and shales, and is intruded by norite sills. It is the oldest sequence of continent-derived sedimentary rocks within the Shyok Suture. It also represents a rare outcrop of the basement rocks to the voluminous Late Cretaceous–Eocene Ladakh Batholith. The Shyok Formation is a younger sequence of volcaniclastic rocks that overlie the Tsoltak Formation and record the Late Cretaceous closure of the Mesotethys Ocean. The petrogenesis of these formations, ophiolite-related harzburgites and norite sill is investigated through petrography, whole-rock geochemistry and U–Pb zircon geochronology. The youngest detrital zircon grains from the Tsoltak Formation indicate Early Cretaceous maximum depositional age and distinctly Gondwanan, Lhasa microcontinent-related provenance with no Eurasian input. The Shyok Formation has Late Cretaceous maximum depositional age and displays a distinct change in provenance to igneous detritus characteristic of the Jurassic–Cretaceous magmatic arc along the southern margin of Eurasia. This is interpreted as a sign of collision of the Lhasa microcontinent and the Shyok ophiolite with Eurasia along the once continuous Shyok–Bangong Suture. The accreted terranes became the new southernmost margin of Eurasia and the basement to the Trans-Himalayan Batholith associated with the India-Eurasia convergence.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5633162

Geochemical evaluation of the in-situ regolith of Madengi hills of Dodoma, Tanzania. Implication on bedrock mapping and delineating gold mineralization target

2021 ◽  
pp. geochem2021-074
Author(s):  
Godson Godfray
Keyword(s):  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Soil Geochemistry ◽  
Residual Soils ◽  
Content Type ◽  
Geochemical Evaluation ◽  
Supplementary Material ◽  
Pathfinder Elements

Successful gold exploration projects depend on a piece of clear information on the association between gold, trace elements, and mineralization controlling factors. The use of soil geochemistry has been an important tool in pinpointing exploration targets during the early stage of exploration. This study aimed to establish the gold distribution, the elemental association between gold and its pathfinder elements such as Cu, Zn, Ag, Ni, Co, Mn, Fe, Cd, V, Cr, Ti, Sc, In, and Se and identify lithologies contributing to the overlying residual soils. From cluster analysis, a high similarity level of 53.93% has been shown with Ag, Cd, and Se at a distance level of 0.92. Au and Se have a similarity level of 65.87% and a distance level of 0.68, hence is proposed to be the most promising pathfinder element. PCA, FA, and the Pearson's correlation matrix of transformed data of V, Cu, Ni, Fe, Mn, Cr, and Co and a stronger correlation between Pb and U, Th, Na, K, Sn, Y, Ta and Be shows that source gold mineralization might be associated with both hornblende gneisses interlayered with quartzite, tonalite, and tonalitic orthogneiss. From the contour map and gridded map of Au and its pathfinder elements, it has been noted that their anomalies and target generated are localized in the Northern part of the area. The targets trend ESE to WNW nearly parallel to the shear zones as a controlling factor of Au mineralization emplacement.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5721965

First evidence for tooth-tooth occlusion in a ctenochasmatid pterosaur from the Early Cretaceous Jehol Biota

2021 ◽  
pp. SP521-2021-141
Author(s):  
Chang-Fu Zhou ◽  
Xinyue Wang ◽  
Jiahao Wang
Keyword(s):  
Early Cretaceous ◽  
Feeding Strategy ◽  
Three Dimensional ◽  
Tooth Wear ◽  
First Record ◽  
Jehol Biota ◽  
Content Type ◽  
Dimensional Reconstruction ◽  
Supplementary Material ◽  
Ct Data

AbstractCtenochasmatid pterosaurs flourished and diversified in the Early Cretaceous Jehol Biota. Here, a partial mandible of Forfexopterus is described based on a three-dimensional reconstruction using high-resolution X-ray Computed Tomography (CT) data. The first nine pairs of functional teeth of the rostral dentition revealed along with their replacements. The functional teeth are evenly arranged with a tooth density of 2.2 teeth/cm. The tooth crown is distinctly reduced from its base to the tip, and framed by two weak ridges, possibly as a pair of vestigial carinae. The replacement teeth are sharp and pointed, and have erupted slightly against the medial surface of the functional teeth. Surprisingly, tooth wear is observed in this specimen, the first record of tooth-tooth occlusion in ctenochasmatids. The wear facets exhibit high-angled lingual and lower-angled labial facets, implying a tooth-tooth occlusion in pterosaur clade. This discovery indicates that the Jehol ctenochasmatids possibly employed a more active feeding strategy than other filter-feeding pterosaurs (e.g. Ctenochasma, Pterodaustro, Gnathosaurus).Supplementary material at https://doi.org/10.6084/m9.figshare.c.5722060

Late Cretaceous granitoids of the Sikhote–Alin orogenic belt, southeastern Russia: implications for the Mesozoic geodynamic history of the eastern Asian continental margin

2021 ◽  
pp. jgs2021-109
Author(s):  
Igor V. Kemkin ◽  
Andrei V. Grebennikov ◽  
Xing-Hua Ma ◽  
Ke-Ke Sun
Keyword(s):  
Late Cretaceous ◽  
Pacific Plate ◽  
Orogenic Belt ◽  
Sikhote Alin ◽  
Asian Continent ◽  
Content Type ◽  
Eastern Margin ◽  
Continental Plate ◽  
Supplementary Material ◽  
Cretaceous Magmatism

We present new U–Pb age data for granitoids in the Central Sikhote–Alin orogenic belt in SE Russia, which refute the established opinion about the absence of the Late Cretaceous magmatism at the eastern margin of the Paleo-Asian continent. It was previously thought that a period of magmatic quiescence occurred from 88 to 50 Ma, related to subduction of the Paleo-Pacific Plate under the eastern margin of the Paleo-Asian continent, although this is inconsistent with evidence from the Sikhote–Alin, Sakhalin, and Japan regions. Three suites of plutonic rocks with different ages were identified in this study. The first suite has ages of 105–92 Ma and formed in a syn-orogenic setting. The second (86–83 Ma) and third (ca. 73 Ma) suites formed during the post-orogenic stage of the Sikhote–Alin orogenic belt. The second and third suites were coeval with Late Cretaceous granitoids that formed in a suprasubduction continental arc known as the Eastern Sikhote–Alin volcanic–plutonic belt (ESAVPB). However, the studied rocks are located far inland from the ESAVPB. The ages of the studied granitoids coincide with the timing of a change in the angle of convergence between the Paleo-Pacific Plate and eastern margin of the Paleo-Asian continent. This change in motion of the oceanic plate with respect to the continental plate was probably caused by a rupture in the subducted slab (i.e., a slab tear), followed by asthenospheric upwelling and partial melting of the overlying crust, which ultimately generated post-orogenic intrusive magmatism.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5738616

Iron and sulphur speciation and cycling in the sediments of marine systems located in the arid environment: Case of the northern Red Sea

2021 ◽  
pp. jgs2021-027
Author(s):  
Valeria Boyko ◽  
Jürgen Pätzold ◽  
Alexey Kamyshny
Keyword(s):  
Red Sea ◽  
Water Depth ◽  
Iron Content ◽  
Gulf Of Aqaba ◽  
Earth System ◽  
Content Type ◽  
Reactive Iron ◽  
The Earth ◽  
Sulphur Cycle ◽  
Supplementary Material

High fluxes of iron minerals associated with aeolian dry deposition may result in anomalously high reactive iron content and fast reoxidation of hydrogen sulphide in the sediments that prevents pyrite formation and results in “cryptic” sulphur cycle. In this work, we studied cycling of iron and sulphur in the deep-water (> 800 m water depth) sediments of the Red Sea and its northern extension, Gulf of Aqaba. We found that reactive iron content in the surface sediments of the Gulf of Aqaba and the Red Sea is high, while the content of sulphur-bound iron is very low and decreases with water depth. The presence of pyrite traces and zero-valent sulfur as well as isotopic compositions of sulphate and pyrite, which are consistent with sulphate reduction under substrate-limiting conditions, suggest that cryptic sulfur cycling is likely to be a result of fast reoxidation of hydrogen sulfide rather than microbial sulfate reduction suppression. In the sediments of Shaban Deep, which are overlain with hyper-saline hydrothermal brine, low reactive iron and high organic carbon contents result in a non-cryptic sulphur cycle characterized by preservation of pyrite in the sediments.Thematic collection: This article is part of the Sulfur in the Earth system collection available at: https://www.lyellcollection.org/cc/sulfur-in-the-earth-systemSupplementary material:https://doi.org/10.6084/m9.figshare.c.5508155

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